This invention relates to assemblies with a movable part and more particularly to an assembly in which the movable part can readily be moved from one position to another and is retained in that position.
More particularly the invention relates to a mounting system for a relatively heavy pivoted member which is regularly pivoted from one position to another whilst in use, such as a visual display unit, which may be pivoted from one position to another by one user or a number of different users.
A common method of permitting such regular pivoting of a relatively heavy member is to have a friction bearing or a handwheel on the pivot. A friction bearing however must have relatively high friction for a heavy member, particularly at high angles of pivot when the centre of gravity of the member is considerably displaced laterally of the pivot. Such high friction can make movement of the member difficult, and regular use can cause wear in the friction member necessitating regular adjustment or renewal of friction pads, washers etc. The use of a handwheel to tighten the pivot after every movement of the member is time consuming and undesirable for the users of a Visual Display unit as variable tightening torque are required with the unit in different positions. A high torques is required, for example, when the unit is at high angles of pivot.
This torque can be reduced by providing a lever extending from the pivot with an arcuate slot at the end of the lever which is engaged by a fixed tightening wheel or nut. Whilst this method does in fact reduce the tightening torque the method is still time consuming and can be dangerous, as too rapid loosening of the wheel or nut can cause the unit to swing rapidly down under its own weight.
Various other methods have been tried to overcome this problem such as the TV camera pivot disclosed in U.S. Pat. No. 4,225,105. This discloses a system of levers and slides arranged so that the camera is moved along a slide as it is pivoted so that the centre of gravity of the camera is always in a position to restore the camera to a horizontal position. A pivot tightening nut is provided to hold the camera in any described position, which again for a visual display unit is undesirable. The arrangement is also quite complex and expensive to produce.